Modern motor vehicles increasingly have so-called hybrid drive devices, to which, in addition to an internal combustion engine, at least one electric machine is available for providing a drive torque. Hybrid drive systems of this type normally include the option to implement a purely electric driving operation in which the internal combustion engine is turned off to save fuel and to reduce pollutant emissions. If the driver of a motor vehicle of this type requires a drive torque which the electric machine alone is unable to make available, the internal combustion engine is started. If the internal combustion engine is started with the aid of the same electric machine which is responsible for the propulsion during electric driving, the torque required for starting the internal combustion engine must be held ready. Also, an instantaneous uphill gradient as a driving resistance may be determined, and internal combustion engine may be started as a function thereof. If the driving resistances increase during the electric driving operation, for example, due to a change in the roadway uphill gradient or due to driving over a curb, the torque requirement for ensuring the propulsion increases. This may be compensated for by the driver by actuating the accelerator pedal as necessary, which causes the internal combustion engine to start. However, a minimum time period elapses before the internal combustion engine is started and the full internal combustion engine torque is available. This has a negative effect on the driving comfort. Depending on the design of the driving device, even an interruption of traction may occur during the start of the internal combustion engine. In particular, on uphill gradients this has a negative effect on the driving comfort.